Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 172045
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
345 PM EST Fri Nov 17 2017

.SYNOPSIS...
High pressure will reside over the region this evening then
shift east of the area later tonight. A strong low pressure
system will track west and north of the area this weekend
bringing rain for Saturday and Saturday night followed by gusty
and colder conditions with lake effect snow by late Sunday.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
High pressure centered over the region late this afternoon will
shift east overnight as low pressure moves into the Illinois/Indiana
area. Skies will be mainly clear through mid/late evening with
just high clouds allowing temperatures to fall initially. Later
tonight clouds will increase with reading expected to be non-
diurnal especially west of I81. Overnight lows will be in the
lower 20s across the western Catskills and western Mohawk Valley
with readings in the mid to upper 20s elsewhere except around
freezing in the Wyoming Valley.

Saturday...A deepening low pressure system will slowly lift
northeast into the central Great Lakes region. Initial short
wave and isentropic lift will spread light rain across the area
during the mid morning to midday period from west to east. The
precipitation on the front edge could be a mix of rain/snow even
though temperatures aloft are warm, evaporative cooling could
bring a brief mix. If this does occur any accumulations would be
only a dusting to a couple of tenths as the precipitation
quickly changes to rain. High will range in the lower to middle
40s.

Saturday Night...Low pressure will lift northeast along the New
York/Canadian border as it continues to intensify. The
GFS/Canadian continue to show a much stronger system than the
NAM and also less progressive. Leaned toward the deeper slower
solution which brings cold air into the area mainly after 12Z
Sunday. Jet dynamics and frontal lift will keep widespread rain
over the area for much of the overnight period then the activity
becomes more showery as the cold front crosses between 06Z-
12Z. Toward daybreak the rain will begin mixing with snow with
light accumulations possible over northern Oneida and Steuben
Counties. Temperatures are expected to hold steady or even rise
slightly during the evening hours then fall rapidly after
frontal passage. By daybreak temperatures will range in the
middle 30s to around 40.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Main concerns in the short term remain focused around the
strengthening low pressure system moving newd through the ern Great
Lakes with strong nw winds and accumulating lake effect snow Sunday
into Monday morning.

By Sunday morning the surface low is expected to be moving into nrn
NY with the wedge of warm air still situated over central NY
and ne PA ahead of the first surface cold front, which will be
rapidly moving to the e/ne. As this occurs, lingering rain showers
will quickly change over to snow. Most of the precipitation will be
in the form of snow by the afternoon.

Temperatures will be falling from the lower 40s in the morning, into
the mid 30s by the afternoon. The initial cold front will be
associated with rapidly cooling temperatures aloft. Steep low level
lapse rates will make conditions very favorable for strong mixing in
a deepening boundary layer. Northwest winds 40 to 50 kt at the top
of the mixed layer will be capable of mixing down to the surface
with sustained winds 20 to 30 mph, and gusts 35 to 50 mph not out of
the question. The strongest winds are expected to be late morning
and early afternoon Sunday. A Wind Advisory will likely be needed
during this time.

The second impact from this system will be the development of lake
effect snow across central NY Sunday afternoon...continuing into
Monday morning. Conditions will become favorable for LES after 5 pm
Sunday as boundary layer winds become unidirectional out of the nw
and the cold air really begins to pour in...850mb temps around -10
to -12 deg C. A 300 deg flow and at least a minor lake to lake
connection, should allow a single LES band to set up Sunday evening
and impact an area from around Auburn to Tully over to Utica,
north...including the Syracuse metro area and I-90 corridor. Most
favorable time should be during the late Sunday evening through the
early morning Monday timeframe. During this period, snowfall rates
may approach 1 to 2 inches per hour for brief times. Snow will
accumulate quickly and cause potentially hazardous travel conditions
Monday morning.

Winds will slowly back to the west and sw into Monday afternoon and
allow the lake band to shift north of the Thruway. As this occurs,
slightly warmer air will begin to move in from the west and will
start to erode the lake effect snow processes and lower the
inversion heights. Snowfall rates will also diminish into the
afternoon, and eventually lift completely to the north out of the
area by the evening. Cloud cover will mix out from south to north
Monday night with quiet weather and cool temperatures.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
A strong push of warm air from the sw is expected Tuesday with
temperatures climbing into the upper 40s and lower 50s. Most of the
day should be quiet before cloud cover increases later in the day
and the next clipper system begins to push in late Tuesday night and
during the day Wednesday with snow showers at night and a mix of
snow and rain during the day. There is some uncertainty with the
pattern later in the week with some of the guidance hinting at weak
ridging behind the departing clipper, and other keeping the
strong/cold cyclonic flow going into the weekend with nw winds and
likely persistent light snow showers...mainly across the central NY
counties. Temperatures will begin a slow decline from the 40s into
the lower to mid 30s for day time highs...and 20s and lower 30s
overnight.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
High pressure over the region will keep VFR conditions over the
terminals through tonight. This afternoon through early evening
just high clouds are expected with increasing mid level clouds
primarily after 06Z. On Saturday, low pressure in the eastern
Great Lakes will bring light rain to the terminals beginning
mid to late morning. Conditions through 18Z will remain
primarily VFR with unrestricted light rain and ceiling around
4K feet. After 18Z conditions will lower into the MVFR/Alternate
Required category in rain.

West/northwest winds around 10 knots with gusts still continuing
until late afternoon at KAVP. Winds becoming light and variable
this evening then becoming southeast late tonight at 5-8 knots.
Southerly winds on Saturday at 10-15 knots.

Outlook...

Saturday night...Widespread restrictions in rain showers mixing
with snow showers.

Sunday / Monday...Variable ceiling restrictions with scattered
lake effect snow showers north, generally VFR south half. Winds
will also be quite strong and gusty Sunday.

Tuesday...Generally VFR.

Tuesday night/Wednesday...Restrictions possible in scattered
rain/snow showers.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

$$
SYNOPSIS...RRM
NEAR TERM...RRM
SHORT TERM...BJT
LONG TERM...BJT
AVIATION...RRM



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